Astronomie - NASA Webb Telescope bekommt seine Gestalt - Update-9

28.12.2016

 

NASA WEBB TELESCOPE STRUCTURE IS SOUND AFTER VIBRATION TESTING DETECTS ANOMALY

 

The 18-segment gold coated primary mirror of NASA’s James Webb Space Telescope is raised into vertical alignment in the largest clean room at the agency’s Goddard Space Flight Center in Greenbelt, Maryland, on Nov. 2, 2016. The secondary mirror mount booms are folded down into stowed for launch configuration. Credit: Ken Kremer/kenkremer.com

NASA GODDARD SPACE FLIGHT CENTER, MD – The James Webb Space Telescope (JWST) is now deemed “sound” and apparently unscathed, engineers have concluded, based on results from a new batch of intensive inspections of the observatory’s structure, after concerns were raised in early December when technicians initially detected “anomalous readings” during a preplanned series of vibration tests, NASA announced Dec. 23. 

After conducting both “visual and ultrasonic examinations” at NASA’s Goddard Space Flight Center in Maryland, engineers have found it to be safe at this point with “no visible signs of damage.”

But because so much is on the line with NASA’s $8.8 Billion groundbreaking Webb telescope mission that will peer back to nearly the dawn of time, engineers are still investigating the “root cause” of the “vibration anomaly” first detected amidst shake testing on Dec. 3.

“The team is making good progress at identifying the root cause of the vibration anomaly,” NASA explained in a Dec 23 statement – much to everyone’s relief! 

“They have successfully conducted two low level vibrations of the telescope.”

“All visual and ultrasonic examinations of the structure continue to show it to be sound.”

Technicians work on the James Webb Space Telescope in the massive clean room at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, on Nov. 2, 2016, as the completed golden primary mirror and observatory structure stands gloriously vertical on a work stand, reflecting incoming light from the area and observation deck. Credit: Ken Kremer/kenkremer.com

Starting late November, technicians began a defined series of environmental tests including vibration and acoustics tests to make sure that the telescopes huge optical structure was fit for blastoff and could safely withstand the powerful shaking encountered during a rocket launch and the especially harsh rigors of the space environment. It would be useless otherwise – unable to carry out unparallelled science. 

To carry out the vibration and acoustics tests conducted on equipment located in a shirtsleeve environment, the telescope structure was first carefully placed inside a ‘clean tent’ structure to protect it from dirt and grime and maintain the pristine clean room conditions available inside Goddard’s massive clean room – where it has been undergoing assembly for the past year. 

NASA’s James Webb Space Telescope placed inside a “clean tent” in Nov. 2016 to protect it from dust and dirt as engineers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland transport it out of the relatively dust-free cleanroom and into a shirtsleeve environment to conduct vibration and acoustics tests to confirm it is fit for launch in 2018. Credit: NASA/Chris Gunn

NASA’s James Webb Space Telescope is the most powerful space telescope ever built and is the scientific successor to the phenomenally successful Hubble Space Telescope (HST). 

The mammoth 6.5 meter diameter primary mirror has enough light gathering capability to scan back over 13.5 billion years and see the formation of the first stars and galaxies in the early universe. 

The Webb telescope will launch on an ESA Ariane V booster from the Guiana Space Center in Kourou, French Guiana in 2018.

“The James Webb Space Telescope is undergoing testing to make sure the spacecraft withstands the harsh conditions of launch, and to find and remedy all possible concerns before it is launched from French Guiana in 2018.”

However, shortly after the vibration testing began technicians soon discovered unexpected “anomalous readings” during a shake test of the telescope on Dec. 3, as the agency initially announced in a status update on the JWST website. 

The anomalous readings were found during one of the vibration tests in progress on the shaker table, via accelerometers attached to the observatories optical structure known as OTIS. 

“During the vibration testing on December 3, at Goddard Space Flight Center in Greenbelt, Maryland, accelerometers attached to the telescope detected anomalous readings during a particular test,” the team elaborated. 

So the team quickly conducted further “low level vibration” tests and inspections to more fully understand the nature of the anomaly, as well as scrutinize the accelerometer data for clues.

“Further tests to identify the source of the anomaly are underway. The engineering team investigating the vibe anomaly has made numerous detailed visual inspections of the Webb telescope and has found no visible signs of damage.” 

“They are continuing their analysis of accelerometer data to better determine the source of the anomaly.”

The team is measuring and recording the responses of the structure to the fresh low level vibration tests and will compare these new data to results obtained prior to detection of the anomaly. 

Work continues over the holidays to ensure Webb is safe and sound and can meet its 2018 launch target. After thoroughly reviewing all the data the team hope to restart the planned vibration and acoustic testing in the new year. 

“Currently, the team is continuing their analyses with the goal of having a review of their findings, conclusions and plans for resuming vibration testing in January.”

Webb’s massive optical structure being tested is known as OTIS or Optical Telescope element and Integrated Science. It includes the fully assembled 18-segment gold coated primary mirror and the science instrument module housing the four science instruments

OTIS is a combination of the OTE (Optical Telescope Assembly) and the ISIM (Integrated Science Instrument Module) together. 

“OTIS is essentially the entire optical train of the observatory!” said John Durning, Webb Telescope Deputy Project Manager, in an earlier exclusive interview with Universe Today at NASA’s Goddard Space Flight Center.

“It’s the critical photon path for the system.” 

The components were fully integrated this past summer at Goddard.

The combined OTIS entity of mirrors, science module and backplane truss weighs 8786 lbs (3940 kg) and measures 28’3” (8.6m) x 8”5” (2.6 m) x 7”10“ (2.4 m). 

The environmental testing is being done at Goddard before shipping the huge structure to NASA’s Johnson Space Center in February 2017 for further ultra low temperature testing in the cryovac thermal vacuum chamber.

The 6.5 meter diameter ‘golden’ primary mirror is comprised of 18 hexagonal segments – looking honeycomb-like in appearance. 

And it’s just mesmerizing to gaze at – as I had the opportunity to do on a few occasions at Goddard this past year – standing vertically in November and seated horizontally in May. 

Each of the 18 hexagonal-shaped primary mirror segments measures just over 4.2 feet (1.3 meters) across and weighs approximately 88 pounds (40 kilograms). They are made of beryllium, gold coated and about the size of a coffee table.

All 18 gold coated primary mirrors of NASA’s James Webb Space Telescope are seen fully unveiled after removal of protective covers installed onto the backplane structure, as technicians work inside the massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland on May 3, 2016. The secondary mirror mount booms are folded down into stowed for launch configuration. Credit: Ken Kremer/kenkremer.com

The Webb Telescope is a joint international collaborative project between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA). 

Webb is designed to look at the first light of the Universe and will be able to peer back in time to when the first stars and first galaxies were forming. 

It will also study the history of our universe and the formation of our solar system as well as other solar systems and exoplanets, some of which may be capable of supporting life on planets similar to Earth. 

 

Up close side-view of newly exposed gold coated primary mirrors installed onto mirror backplane holding structure of NASA’s James Webb Space Telescope inside the massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland on May 3, 2016. Aft optics subsystem stands upright at center of 18 mirror segments between stowed secondary mirror mount booms. Credit: Ken Kremer/kenkremer.com


Watch this space for my ongoing reports on JWST mirrors, science, construction and testing. 

 

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news. 

Ken Kremer

Ken Kremer/Universe Today reflecting in and about the golden mirrors of NASA’s James Webb Space Telescope which will peer back 13.5 Billion years to unravel the mysteries off the formation of the early Universe and tell us how our place in the Universe came to be. Credit: Ken Kremer/kenkremer.com

Quelle: Universe Today

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Update: 4.01.2017

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NASA's Webb Telescope to Resume Vibration Testing in January

JWST sits in a clean tent before vibration testing at NASA Goddard
NASA's James Webb Space Telescope sits in a clean tent before vibration testing at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Credits: NASA's Goddard Space Flight Center/Chris Gunn
computer graphic rendering of JWST
Computer graphic rendering of NASA's James Webb Space Telescope
Credits: Northrop Grumman

Vibration tests are one of the many tests that spacecraft and instruments endure to ensure they are fit for spaceflight. During routine testing of NASA's James Webb Space Telescope, an unexpected response occurred from several of the more than 100 devices designed to detect small changes in the motion of the structure. This prompted the engineers put the vibration tests on hold to determine the cause.

Since then, the team of engineers and scientists have analyzed many potential scenarios for the measured responses. They are closer to pinning down the cause, and have successfully conducted three low-level vibrations of the telescope. 

 

All visual and ultrasonic examinations of the structure continue to show it to be sound.

 

"Currently, the team is continuing their analyses with the goal of having a review of their findings, conclusions and plans for resuming vibration testing in January," said Eric Smith, program director for NASA's James Webb Space Telescope, NASA Headquarters in Washington.

 

"This is why we test -- to know how things really are, as opposed to how we think they are," said Paul Geithner, deputy project manager – technical for the Webb telescope at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

 

During the vibration testing on Dec. 3 at NASA Goddard, accelerometers attached to the telescope detected unexpected responses and consequently the test shut itself down to protect the hardware.

 

The test shut itself down in a fraction of a second after a higher-than-expected response was detected at a particular frequency of vibration, about one note lower than the lowest note on a piano.

 

 

At NASA, vibration and acoustics test facilities provide vibration and shock testing of spaceflight hardware to ensure that functionality is not impaired by severe launch and landing environments. Launches create high levels of vibration in spacecraft and equipment and ground testing is done to simulate that launch induced vibration. Vibration testing is done on components as small as a few ounces to as large as complete structures or systems.

 

By performing the vibration testing on NASA's James Webb Space Telescope, scientists and engineers can ensure that the spacecraft and all of its instruments will endure the launch and maintain functionality when it is launched from French Guiana in 2018.

 

"The Webb telescope is the most dynamically complex test article ever tested at Goddard, so the responses were a bit different than expected," Geithner said.

 

Further testing may or may not reveal additional unexpected responses, but that is the purpose of these tests. If additional anomalies are detected, they can be corrected before launch.

Quelle: NASA

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Update: 25.02.2017

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Closing in on launch: NASA’s gold-mirrored, $8 billion Webb Space Telescope

 
 
 
 
 February 24 

The world’s most expensive telescope is parked for the moment in Greenbelt, Md., shrouded in a protective tent at the NASA Goddard Space Flight Center. In just two years, this long-delayed, $8 billion, cosmos-penetrating instrument is supposed to be nearly a million miles from Earth.

If it works, the James Webb Space Telescope will collect the oldest light in the universe, emitted soon after the big bang, when the first stars lit up and the first galaxies began to form. It will study black holes lurking at the center of galaxies. It will scrutinize the light from planets around distant stars and look for atmospheres you’d expect to see on worlds rioting with life.

But that’s only after an epic journey. It’s not a straight shot from the Washington suburbs to space.

The telescope first must be sealed in a climate-controlled container. Then, sometime in late March or early April, a truck will haul it very slowly and gently in the dead of night along a partially closed Capital Beltway. A lead car will watch for road obstacles and potholes.

Arriving at Joint Base Andrews, the Webb should slide, barely, into the cargo hold of a C-5C military transport plane.

Then comes a flight to Houston, to the NASA Johnson Space Center, where it will be tested in a vacuum chamber that will simulate the environment of deep space. From Houston it will be flown to Los Angeles, to a facility run by the project’s primary contractor, Northrop Grumman, where it will be mated with its sunshield and navigational hardware.

Then comes a boat ride, one that will carry the telescope down the southwestern coast of North America and through the Panama Canal to French Guiana. That’s where, in October 2018, it will be blasted into space atop a European Ariane rocket — a quarter-century after the Webb was conceived.

What could go wrong?

“It’s wonderful and terrifying,” says astronomer Heidi Hammel of the Association of Universities for Research in Astronomy, one of six scientists guaranteed observing time with the instrument. “The terrifying part comes because we know that this is rocket science for real, we are taking our fabulous telescope — it’s a beautiful machine — and we’re going to put it on a rocket ship and light the fuse.”

 

Astronomers have a complicated and anguished relationship with the Webb. It’s amazing. It’s also wildly expensive. And it was supposed to be in space years ago.

John Mather, a Nobel laureate who is the senior project scientist, began working on it in 1995. He and his team had to achieve a long list of innovations to get the Webb built — things like the gold-covered mirrors, the sunshield and the means of keeping everything very cold.

“This job was just so hard, and when you’re at the beginning you don’t have the imagination to see how hard it is. No one had appreciated the difficulty of the test program,” he said this week.

This telescope can see back in time, almost to the beginning of our universe

 

Cost overruns led to budget reviews, battles in Congress, near-death experiences, recrimination and, finally, to a reconfigured budget and timetable that lawmakers approved. The project devoured NASA money that might have gone to other science endeavors. It became known as the telescope that ate astronomy.

The Webb, which includes major contributions from the Canadian and European space agencies, has long been seen as the successor to the Hubble Space Telescope. The latter is still working fabulously but getting long in the tooth.

There have been rumors that the Trump administration could somehow gin up a Hubble repair mission with astronauts on a new shuttle-like spacecraft, but officials at NASA Goddard say they haven’t been asked to plan for anything like that.

The Webb is quite different from the Hubble, starting with the fact that it’s much bigger. The Hubble has a 2.4-meter mirror, but the Webb has 18 hexagonal mirrors that collectively are 6.5 meters — more than 21 feet — in diameter. It can collect seven times as much starlight.

The new telescope can observe the universe in infrared wavelengths of light that are inaccessible to the Hubble. In deep space, shaded from the sun, the Webb is designed to operate under extremely cold conditions. That’s necessary for infrared astronomy because otherwise the heat from its instruments would block out the faint light from distant objects.

 

As things turned out, the Webb’s problems with schedule may have been fortuitous.

The original goal was to look at very faint objects in deepest space — the very first stars and galaxies, so far away that their light, emitted about 13.7 billion years ago, is only now reaching our solar system. But the Webb may play a key role in the search for habitable worlds that are relatively nearby, orbiting stars in our own galactic neighborhood.

The very first “exoplanet” — a planet orbiting another star — was discovered 22 years ago, right about the time Mather began working on the Webb. Thousands of exoplanets have been found since.

Earlier this week, astronomers announced the remarkable discovery of a system with seven Earth-size planets around a star named Trappist 1, some 39 light-years away. Several have orbits that might allow water, if present, to be liquid at the surface.

There’s no way for the Webb or any other current telescope to see these planets directly, because they’re too close to the parent star. But as they transit the star — passing across the face of the star as seen from the telescope — the starlight will dim slightly. That’s how they were discovered.

An atmosphere around a planet will skew the wavelengths of the starlight. Astronomers can then use spectroscopy to discern which kinds of molecules make up the exoplanet atmosphere.

The Hubble has looked at the Trappist system and already has determined that the planets are probably rocky rather than gaseous like Jupiter or Saturn. But the Webb has sophistication the Hubble lacks. The Webb can detect the clear signatures of atmospheres containing water, ozone, oxygen, methane and other molecules. That could provide compelling evidence of a habitable planet.

As astrophysicist Michelle Thaller of NASA points out, while it wouldn’t be the same thing as direct detection of life, it would be a major achievement for the still-young scientific field known as astrobiology.

 

Closer to home, the Webb’s prime viewing targets include the Great Red Spot of Jupiter, Saturn’s intriguing moon Titan, the dwarf planet Pluto and its moon Charon, plus the gaggle of “trans-Neptunian objects” way out in the exurbs of the solar system — little-known worlds such as Sedna, Quaoar and Makemake.

But first the telescope, which is supposed to begin observing in April 2019, has to function as planned. It would be hard to repair something parked at L2, the Webb’s destination point in space, which is 930,000 miles from Earth on the opposite side of our planet from the sun.

“I can tell you that we’re doing what we need to do to make sure that it’ll work,” Mather said. “You test. And test and test.”

And look for potholes along the way — literally.

Quelle: The Washington Post

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NASA's Webb Telescope Team Prepares For Earsplitting Acoustic Test

Inside NASA's Goddard Space Flight Center in Greenbelt, Maryland the James Webb Space Telescope team completed the environmental portion of vibration testing and prepared for the acoustic test on the telescope. Engineers and technicians pushed the telescope (wrapped in a clean tent) through a large set of insulated steel doors nearly a foot thick into the Acoustic Test Chamber, where the telescope will be exposed to the earsplitting noise (and resulting vibration) of launch. These photos show the telescope inside (top) and outside (bottom) the acoustics chamber.

 

The James Webb Space Telescope is the scientific successor to NASA's Hubble Space Telescope. It will be the most powerful space telescope ever built. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

 

The James Webb Sapce Telescope outside the acoustics chamber at NASA's Goddard Space Flight Center in Greenbelt, Md.
The James Webb Sapce Telescope inside the acoustics chamber at NASA's Goddard Space Flight Center in Greenbelt, Md.
Credits: NASA/C. Gunn
The James Webb Sapce Telescope inside the acoustics chamber at NASA's Goddard Space Flight Center in Greenbelt, Md.
The James Webb Sapce Telescope outside the acoustics chamber at NASA's Goddard Space Flight Center in Greenbelt, Md.
Credits: NASA/C. Gunn
Quelle: NASA
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Update: 15.03.2017
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NASA's Webb Telescope Ghostly 'Lights Out' Inspection

The clean room lights were turned off to inspect the telescope after it experienced vibration and acoustic testing. The contamin

What happens when the lights are turned out in the enormous clean room that currently houses NASA's James Webb Space Telescope? The technicians who are inspecting the telescope and its expansive golden mirrors look like ghostly wraiths in this image as they conduct a "lights out inspection" in the Spacecraft Systems Development and Integration Facility (SSDIF) at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

 

The clean room lights were turned off to inspect the telescope after it experienced vibration and acoustic testing. The contamination control engineer used a bright flashlight and special ultraviolet flashlights to inspect for contamination because it's easier to find in the dark.

 

NASA photographer Chris Gunn said "The people have a ghostly appearance because it's a long exposure." He left the camera's shutter open for a longer than normal time so the movement of the technicians appear as a blur. He also used a special light "painting" technique to light up the primary mirror.

 

The James Webb Space Telescope is the scientific successor to NASA's Hubble Space Telescope. It will be the most powerful space telescope ever built. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Quelle: NASA

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Update: 31.03.2017

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James Webb telescope: Hubble successor set for yet more tests

JWSTImage copyrightNASA
Image captionJWST has just emerged from vibration and acoustic investigations

Engineers are getting ready to box up the James Webb Space Telescope and send it to Houston, Texas.

The successor to Hubble, due for launch in 2018, is going to be put inside the giant thermal vacuum chamber where they tested the Apollo spaceships.

For 90 days, JWST will get a thorough check-up in the same airless, frigid conditions that will have to be endured when it eventually gets into orbit.

The telescope's aim will be to find the first stars to shine in the Universe. 

To achieve this goal, the observatory is being given an enormous mirror and instruments that are tuned to detect some of faintest objects on the sky.

James Webb Space Telescope

More than two decades in development, JWST is currently passing through the most critical phases on its construction timeline.

Any major technical hiccups now would seriously derail its launch readiness. 

The past year has seen the assembly of the main telescope structure, with its 18 beryllium-gold mirror segments, at the US space agency's (Nasa) Goddard centre in Greenbelt, Maryland.

Attached to this structure are Webb's four observing instruments, which sit inside a cage on the rear of the big reflector.

MirrorImage copyrightNASA
Image captionThe telescope structure was assembled at the Goddard Space Flight Center

The whole edifice has just gone through vibration and acoustic testing at Goddard. This has simulated the shaking and the roar of the carrier rocket. This will be an Ariane 5 provided by project partner, the European Space Agency. 

One vibration run had to be stopped early when unexpected accelerations were detected in the region of the telescope's secondary mirror, but the analysis concluded it was not an issue of significant concern. So far, so good.

Now, JWST must fly to Nasa's Johnson centre at the end of April, or perhaps the beginning of May. 

There, it will enter the famous Chamber A. This is the largest testing facility of its kind in the world, and the only one capable of housing an orbiting telescope on JWST's scale. 

Chamber AImage copyrightNASA
Image captionChamber A is the facility that ran the rule over Apollo hardware

Engineers want to know that Webb's mirrors and instruments will function in unison when they are sitting out in space.

The chamber will provide important evidence of that by going super-cold (it can go as low as minus 260 Celsius).

An artificial light source shone on to Webb will ensure everything lines up as it should.

"When we are at temperature, we will unfold the mirrors and move them," explained JWST instrument systems engineer Begoña Vila. 

"On orbit, not only do they have to unfold, you have also to confirm the focus for the different instruments. 

"If you think about it, with those 18 segments we start with 18 different images of a star, and so we have to move all those images until we have a single one and it is in focus. It's that process that we have to practise," she told BBC News. 

Mirror size comparison

This work should complete in the autumn, but there will be no hiatus in the schedule. Webb will immediately go to Los Angeles to the aerospace company Northrop Grumman.

It is in California where the final elements of the observatory are being put together. 

These are the satellite bus, which incorporates the computers, the power and propulsion systems, etc, needed to control Webb in space; and a tennis-court-sized sunshield.

JWST will look at the cosmos in infrared light and so needs to be shaded from the glare and heat of the Sun.

Bus and shield are in their end stages of assembly. Some final components still have to be attached, such as a boom that will deploy the shield once in space, but Northrop Grumman anticipates everything being in position to receive the telescope structure and instruments when they turn up for final integration. 

SunshieldImage copyrightNORTHROP GRUMMAN
Image captionThe shield and satellite bus will be attached to the telescope structure in Los Angeles

The finished observatory's journey from LA to the Ariane launch pad in Kourou, French Guiana, will be made by boat.

This is earmarked to begin about six months before the currently slated November 2018 lift-off.

"At this point we are in good shape," confirmed Eric Smith, JWST's programme director and programme scientist. 

"We have about five months of scheduled reserve. That's more than is typical for a programme at Nasa but we recognise that this programme is very large and so we know we need to have a little more.

"It's amazing how fast everything is going at this point. But I keep telling people this is the part where you're going to keep finding problems because even though you've tested things all the way up, when you finally put it together some of those things behave just a little bit differently to how you were expecting. 

"It's exciting but, boy, it's moving fast," he told BBC News.

Chamber AImage copyrightNASA
Image captionEngineers have already simulated the chamber testing with a model telescope
Quelle: BBC

 



 

 

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